1. Field of the Invention
The present invention relates to rotation rate measuring fiber optic Sagnac interferometers of the closed control loop type. More particularly, this invention pertains to a method for compensating light source wavelength variations in such an interferometer.
2. Description of the Prior Art
The scale factor of a fiber optic Sagnac interferometer for measuring rotation rate that includes a closed control loop is wavelength-dependent. Fiber optic gyros that employ digital phase ramp resetting, for example those described in U.S. Pat. Nos. 5,123,741 and 5,351,123, minimize light source wavelength (and, thus, scale factor) variation by both indirect and direct methods. Indirect methods involve light source temperature and injection current stabilization. Direct processes employ supplemental optical components (e.g. gratings, interferometers) to measure the wavelength of the light source. A direct process of the above-described type is disclosed in U.S. Pat. No. 5,311,279. Indirect stabilization involving temperature regulation cannot account for effects due to light source aging. Direct processes, on the other hand, require both supplemental optical components and related modification of associated electronic systems.